fix: add withdrawal validation with balance and liquidity checks (#89)

[Emeka-12]

Problem this solves

The withdrawal form on the Sponsors page validates only that the share amount is a positive number. It never checks the requested shares against the sponsor's actual share balance or against the pool's available liquidity. This leads to sponsors signing and submitting transactions that are guaranteed to fail on-chain, and the Preview Value block quotes payouts for shares the user does not own.
Closes #89

What was built

• GET /liquidity/my-summary — Added \getMySummary()\ to \sponsors.service.ts\ with typed \MySummary\ response in \ ypes/index.ts. No API calls in the page file.
• Position query — Fetched in \Sponsors.tsx\ with TanStack Query (matching the existing \poolInfo\ pattern), enabled only when the wallet is connected.
• Over-balance validation — Blocks submission and shows an inline error when requested shares exceed the sponsor's balance.
• Over-liquidity validation — Blocks submission and shows its own distinct inline error when the estimated payout exceeds \poolInfo.availableLiquidity.
• Max button — Fills the input field with the sponsor's full share balance.
• Preview suppression — The Preview Value block is hidden when the amount fails validation.
• Loading/error/empty states — Button disabled while position loads. Query failure shows an error card. Zero-share sponsors see an empty state.
• Submit button — Disabled when any validation error exists, while position is loading, or when the amount is not positive.
• Tests — 13 new tests covering over-balance, over-liquidity, exact-balance boundary, zero-share sponsor, Max button, preview suppression, loading state, error state, and not-connected state.

How it was tested

• 
  pm run build\ — passes with zero errors
• 
  pm test\ — all 49 tests pass across 10 test files (13 new tests added)
• Manual verification of each validation state via unit tests

Files touched

• \src/pages/Sponsors.tsx\
• \src/services/sponsors.service.ts\
• \src/services/queryKeys.ts\
• \src/types/index.ts\
• \src/pages/tests/Sponsors.test.tsx\
• \src/lucide-react.d.ts\ (pre-existing missing declaration fix)
• \context/progress-tracker.md\

Closes #89

[EmeditWeb]

great job, LGTM